1. Field of the Invention
This invention relates to a process of cold forming a shell core in a manner utilizing binder coated granular material hardened through the introduction of catalyst gas wherein the shell core is originally formed by the joining of hollow preformed core portions and wherein such joining occurs through the performance of a fusion process so as to define a one piece integral shell core eliminating the need or usage of investment hole in the outer surface or wall portions of the shell core.
2. Description of the Prior Art
In the formation of a foundry product, and in particular hollow foundry products such as shell cores, conventional methods have generally involved the application of heat in the hardening of the sand or granular material forming the shell core. The use of such heat obviously has disadvantages due to the increased cost of fuel or energy to create such heat. Such prior art process also have inherent problem of taking a long curing times resulting in greater overhall production time in producing the desired shell cores.
In recent years methods have been developed utilizing a cold forming process whereby the requirement of large amounts of heat and therefore energy is eliminated. In such processes a catalyst gas is exposed to granular material or sand having a binder coating thereon. Such exposure results in reaction of the binder and certain resins contained therein to cause a hardening of the granular material into a predetermined configuration, as desired.
In the formation of hollow or shell cores prior art process normally involve the inclusion in the outer wall of the formed cores of an investment hole. This investment hole was required to remove the unhardened sand or granular material from the interior of the core. As can readily be appreciated the larger the intended core the greater difficulty was encountered in handling the core due to the increased weight, etc. Also more material was required in forming such prior art core products because of the need to fill the entire interior of the core, harden the exterior "shell" and then remove the unhardened granular material from the interior of the formed core.
Accordingly, there is an obvious need in the foundry industry for the formation of a shell core product utilizing a cold forming process or technique and eliminating the problems associated with removal of the unhardened portions of the interior through an investment hole, etc.
Such a process would have the advantages of shorter production time, use of less material, ease of handling because of lighter weight of the formed product and overall increase in the quality of the product due to the elimination of any investment hole structure.